In vehicular applications, a typical four-wheel steering system steers the front and the rear wheels of a vehicle. More specifically, a rear wheel steering porition of the system may produce a desired rear wheel steering angle to improve directional stability at high speeds and maneuverability at low speeds. The high-speed steering method may reduce vehicle yaw by steering the, front and rear wheels in the same general direction, and thereby improve vehicle stability. The low speed steering method may achieve tight turning radii at low speeds by steering the front and rear wheels in different directions to thereby reduce the effective turning radius of the vehicle.
Use of a vehicle for the towing of a trailer, for example, may affect the optimal ratios between the front and rear wheel steering angles. For vehicles that are frequently used for towing, such as some trucks, for example, it may be desirable to provide a driver-selectable steering mode that retains the many benefits of four-wheel steering while compensating for the presence of a trailer.
The above described and other features are exemplified by the following Figures and Description in which a method for controlling a four-wheel steering system of a vehicle is disclosed that includes recognizing a driver-selectable mode, receiving a signal preferably indicative of a front wheel steering-angle, and determining a rear-to-front steering-angle ratio in correspondence with the recognized mode and the received signal; and optionally includes receiving a signal indicative of vehicle speed, recognizing a current system state, determining a desired steering-angle, generating a command based on the desired and received steering-angles and the recognized system state, and diagnosing conditions in accordance with the received signals in order to enter an output disabled mode.